Trailer Brake Controller Information

An electric trailer brake controller is a device that installs in the cab of your tow vehicle and activates your trailer's electric or electric-over-hydraulic brakes when you hit the brakes in your tow vehicle. Many models are available, and they differ from how they look to the number of brakes they can power. But all of them can be divided into 2 main groups: proportional or time delayed.

A proportional brake controller senses how the tow vehicle is slowing or stopping and applies the trailer's brakes with the same intensity. So if you slam on the brakes in your tow vehicle, the controller will activate your trailer's brakes just as forcefully. With a proportional controller, you can adjust the initial braking power and aggressiveness based on your trailer's weight and your braking preferences.

A time-delayed brake controller activates the trailer's brakes with a preset intensity (power output) and rate of application (sync), both of which are determined by you. With this type of controller, there is a delay between the time that you initially apply the brakes in your tow vehicle and the time that the controller reaches maximum power output to the trailer's brakes. However, this delay can be adjusted with the sync setting.

Choosing a Trailer Brake Controller

Proportional Brake Controllers

With a proportional brake controller, you can get heavy-duty emergency braking, general braking, or slow-to-an-idle braking for your trailer automatically. The intensity with which your trailer brakes are activated and the rate at which they are applied are dependent on the deceleration of your tow vehicle. This means that, unlike time-delay controllers - which send the same amount of preset power to your trailer brakes every time - proportional controllers are able to adapt to every braking situation differently. So if you slam on the brakes in your truck, your trailer brakes will activate with the same extreme intensity. And if you merely slow down as you approach a red light, your trailer will gradually brake in the same manner.

A proportional brake controller senses when and how your tow vehicle brakes by means of an accelerometer or an internal inertia-based sensor. The accelerometer or sensor responds to the deceleration of your tow vehicle as you brake by signaling the controller to send out enough power to your trailer brakes so that they are activated with an intensity that matches. The result is uniform braking across your towing setup. No push-pull action - just smooth, proportional braking every time.

Pros

• Smooth, quick braking
• Less wear on both vehicle and trailer brakes
• Increased braking efficiency

Cons

• More expensive than time-delayed controllers (though the cost difference between the 2 types has been decreasing)
• Not as easy to install as a time-delayed controller

Time-Delayed Brake Controllers

A time-delayed brake controller applies your trailer's brakes when the brake pedal in your tow vehicle is engaged. Every time you apply the brakes in your tow vehicle, a signal is sent - via the brake switch - to the brake controller. The controller then sends power out to your trailer brakes to activate them with an intensity set by you, at a rate determined by you. Both the amount of braking power (output) and rate of application (sync) can be adjusted to suit your preference, the road conditions, type of trailer, and size of the load. To determine which levels are best for your application, you must test out your towing setup and choose what feels best.

A time-delay controller is so named because there is a delay between the time that you initially apply the brakes in your tow vehicle and the time that the controller reaches maximum power output. Unlike a proportional brake controller, which activates your trailer's brakes based on the deceleration of your tow vehicle, a time-delayed controller sends power out in the same way, with the same gradual delay, no matter the braking situation. Although this delay always exists, it can be adjusted by changing the sync setting.

A time-delayed brake controller doesn't rely on sensing the braking motions of the tow vehicle. This allows you to mount the controller at any angle.

Most time-delayed brake controllers can allow the brakes to pulse on and off when the hazard flashers are activated and the brake controller is set aggressively. This happens because power from the brake lights can feed back into the brake controller. A pulse preventer can isolate the brake controller from the flashers and will eliminate this problem. Pulsing of the brakes when the hazard flashers are in use is not usually a problem for vehicles that have a different bulb for the stop and turn signals. You can usually identify a vehicle that has separate stop lights and turn signals because it will have amber turn signals.

Pros

• Easy to install - can be mounted at any angle
• User friendly
• Low profile

Cons

• Uneven brake wear between tow vehicle and trailer
• Chance of brake pulsing when hazard flashers are used

Proportional Brake Controllers vs. Time-Delayed

Similarities:

• Allow the user to adjust the maximum braking power to match the weight of the trailer being pulled
• Have a manual override trigger that can be used to apply only the trailer brakes
• Have the same wiring configuration for installation

Differences:

• Cost: Time-delayed controls are typically less expensive, although recent advances in proportional brake controls have narrowed the cost difference.
• Braking performance: Time-delayed controls always send the same braking power to the trailer brakes. Proportional brake controls will vary the braking power based on how quickly the tow vehicle is stopping, which produces a smoother braking action.
• Wear and tear: Time-delayed brake controls cause more wear on either the trailer or vehicle brakes because one or the other will be doing the majority of the braking. Proportional controls reduce wear by spreading the braking power evenly.
• Mounting: Time-delayed brake controls can be mounted in any position and at any angle. Proportional controls will typically need to be mounted within a certain range, such as within 70 degrees of level, to work properly.
• Calibration: Time-delayed brake controls typically will not require calibration. Some models of proportional brake controls need to be calibrated to work properly. However, most of the newer models are self-calibrating or have a very simple calibration, so they are nearly as easy to set up as time-delayed models.
• Size: Time-delayed brake controls have traditionally been smaller and slimmer than proportional controls, but newer models of proportional controls come in shapes and sizes very similar to time-delayed controls.
• Use: Time-delayed brake controls are best for the casual user. Proportional controls should be considered if the trailer will be towed often because these controllers operate well in diverse towing conditions and produce less wear on the braking systems of the tow vehicle and trailer.
• Safety: Proportional brake controls provide an additional level of safety because they will automatically ramp up to full power if the tow vehicle makes an emergency stop.

Wiring Diagram for Typical Brake Control Installation

For more information about installing a trailer brake controller, see etrailer.com's article Brake Controller Installation: Starting from Scratch.

For more information about installing a 7-way connector, see etrailer.com's installation guide Brake Controller 7- and 4-Way Installation Kit (ETBC7).

Four wire connnections are required for installation of a brake controller.

1. Trailer feed (usually blue): This wire connects the brake controller to the 6-way or 7-way trailer connector at the back of the tow vehicle. Some vehicles with factory tow packages already have a wire for this connection, and it would run from under the dash to the rear of the vehicle. Otherwise, you will need to run a wire from the brake connector location, underneath the vehicle, through the firewall, then to the desired brake control mounting location. Most vehicles already have a pre-existing hole or grommet to get through the firewall. However, if your vehicle doesn't have a pre-existing hole, you will have to drill.
2. Ground (usually white): This wire is connected from the brake controller to any reliable ground location.
3. Brake switch (usually red): This wire can be found at the switch at the top of the brake pedal. Usually more than 1 wire runs out from the switch, and you will have to test them with a circuit tester to determine which wire has power when the brake pedal is depressed. Use a quick-splice connector to tap into this wire.
4. Battery power (usually black): This wire connects power from your tow vehicle's battery to the brake controller. Some vehicles with factory tow packages already have this wire run from under the dash to the battery with some kind of circuit protection. Otherwise, a wire must be run through the firewall and connected directly to the battery with an in-line circuit breaker.

Wiring Color Guide for Factory Brake Control Wiring Harness

If your vehicle is equipped with a factory tow package (ie, there is a 7-way trailer connector at the rear of your vehicle), a vehicle-specific brake control wiring adapter may be available for your vehicle. With a custom adapter, the brake controller installation will be simple: just plug one end of the adapter into the controller and plug the other end into the factory connector under your vehicle's dash.

If a custom wiring adapter is not available for your vehicle, then you'll have to install the brake controller with a universal wiring harness. This harness will plug into the controller at one end, and then you'll have to splice the other end into the existing wiring on your vehicle. The chart below will help you match wire colors from the brake controller to your vehicle.

Note: Vehicle manufacturers change wiring configurations regularly, so use a circuit tester to verify all connections.